The present invention relates to an electrical connector having two mating assemblies that eject from one another as a result of a tug on a power cord connected to at least one of the connector assemblies.
Appliance cords present safety hazards when accidentally subjected to pull forces. Often users will manually pull on a typical 6-foot or 8-foot cord extending from an appliance resulting in abnormal forces at the wall outlet and/or damage to the cord, the outlet, or the appliance itself. It has been reported that on many occasions children have been injured by pulling a hot coffee pot or other similar electrical appliance down on themselves. In other instances, one tripping over a cord may pull the appliance from the shelf.
U.S. Pat. No. 5,480,313 describes an automatic disconnect mechanism for an electrical terminal fitting including a single assembly that springs from electrical engagement with a mating fitting, such as an existing fixed wall socket or the like, in response to a pull on an associated electrical cord. The single assembly includes both the spring to cause separation of the two mated terminal fittings and a trigger mechanism that is actuated by pull forces on the cord to trigger the separation. The mechanism requires the user to pre-set the trigger release which is not automatic. The mechanism does not have a self-locking mechanism actuated upon initial engagement of the terminal fittings. The mechanism generally requires a firm wall socket or other base from which to push-off when disconnecting. The disclosure includes a description of a dangerous situation that can arise with one embodiment in an application to a vehicle under battery charge, where one end would necessarily be left dangling with exposed electrical terminals. In the described situation, although the fitting containing the spring assembly actuates as the vehicle moves off, the electrical prongs of the mating plug fitting are left protruding and electrically exposed.
U.S. Pat. No. 4,114,969 discloses a plug release mechanism designed for use at the plug end of an electrical cord to interact with the structure surrounding a wall outlet in which the plug end is engaged. The device requires manual setting a cam-like actuation rod before use. The device relies on a wall socket-to-plug release in an axial force direction during a tug on the cord. The device does not provide a positive locking mechanism. The device is not designed for application at the appliance, or in-line on a cord.
What is needed is a device that would allow breakaway at an appliance during a tug on the cord. What is also needed is a device with the ability to have a positive locking mechanism while in place. What is also needed is a device that would not present a safety exposure situation when disconnected. What is also needed is a device that would have flexibility of design to allow interfacing to various types of outlets, appliances and yet be simple to manufacture.
The present invention resolves these problems and satisfies these needs. The present invention provides a quick release breakaway mechanism. The present invention also provides a design that leaves neither end with protruding terminals after disconnecting or when it is in a disconnect state. The present invention also provides a locking mechanism which provides the user with a positive feedback as to when the locking mechanism is engaged. The present invention also can be easily manufactured and is adaptable to many types of appliances, wall outlets and other uses.
The main aspect of the present invention is to provide a breakaway electric cord mechanism that can be used in connection with the base of an appliance. The term appliance as used herein is not limited to those kitchen appliances that might be easily supported by a counter top, but is also intended to refer broadly to other objects that are typically connected to a conventional wall plug by a length of electric cord, which cord presents the potential for injury or damage to property. The major components are a plug assembly, and engagement mechanism, and a base assembly. The term plug assembly is used here to refer in the most general sense to an assembly attached to or integral with one end of an electrical cord, the electrical cord having a plug for insertion into a conventional wall socket to provide a source of power. The term base assembly is used here to refer in the most general sense to an assembly designed to mate with a corresponding plug assembly in conjunction with the engagement mechanism of the present invention. The base assembly will generally be directly electrically connected to an electrical power consumption unit of an electrical appliance. These assemblies act in conjunction to provide a spring release of the assemblies from each other in the event of a tension, for example a tug, being applied to the cord greater than a preset minimum level sufficient to allow disengagement of the engagement mechanism. Since the plug assembly is separable from the base assembly, the separate assemblies can be color coordinated with each other. The plug assembly can be manufactured in a variety of color options to allow the consumer to match each portion of the assembly with the expected decorative environment in which the electrical appliance is to be employed.
In the most general case, the invention can be viewed as an electrical connector comprising a first assembly including a housing defining a cavity containing prongs suitable for connection to one portion of an electrical power delivery system, and an ejection plunger; a second assembly including a case containing electrical contacts for electrical connection with the prongs, the contacts being suitable for connection to another portion of the electrical power delivery system; and an engagement mechanism coupled to one of the first and second assemblies and engaging another of the first and second assemblies during a connection between the first and second assemblies, the engagement mechanism being releasable in the event of a tug on either assembly thereby enabling the ejection plunger to separate the first assembly from the second assembly.
More particularly, the invention can be viewed as an electrical connector comprising a first assembly including a housing defining a cavity containing prongs suitable for connection to one portion of an electrical power delivery system, and an ejection plunger; a second assembly including a case containing electrical contacts for electrical connection with the prongs, the contacts being suitable for connection to another portion of the electrical power delivery system; and a holder coupled to the second assembly and containing slidable receptacles for engaging the prongs of the first assembly and the electrical contacts of the second assembly, the holder carrying an engagement mechanism for engaging the cavity of the first assembly during a connection between the first and second assemblies, the second assembly being movable over a predetermined range relative to the holder in the event of a tug on either assembly thereby allowing disengagement of the engagement mechanism and enabling the ejection plunger to separate the first assembly from the holder and second assembly.
The first or base assembly includes a housing including a plug-receiving cavity. A set of prongs are situated wholly within the plug-receiving cavity of the housing so as not to project outward from the housing. The prongs can be electrically connected to the electrical power consumption unit of an electrical appliance by way of retention screws provided at a rear end of the base assembly. The ejection plunger or thrust mechanism consisting generally of a thrust spring and thrust spring plunger is located centrally within the base assembly. The thrust spring and thrust spring plunger are respectively contained within the base assembly housing via a slot or opening into which a plunger spring retention plate is fastened with two screws. The thrust spring plunger has tabs that extend laterally outward to prevent the thrust spring plunger from coming free from the base assembly housing under influence of the outward force of the thrust spring. Once assembled, the appliance base assembly contains the non-protruding contact pins and the thrust spring plunger in an extended position. The plunger resists the entrance of any foreign object between the contact pins. The thrust spring, in a non-compressed mode, can extend the thrust spring plunger beyond the extent of the electrical prongs within the assembly housing. The thrust spring plunger is preferably manufactured of a non-conductive material. The base assembly cavity also contains a recessed groove that captures the engagement mechanism.
The second assembly or plug assembly is a one-piece molded assembly consisting generally of a power line cord, conductive electrical contact pins electrically connected to the power line cord, and a non-conductive case. The power line cord can include a standard wall plug connector at one end, or can have a specialty connector if so desired. The electrical contact pins are preferably similar in design to standard electrical plug prongs, but could have special conformation, if required. The body or case also includes external tabs or positive snaps for mating with the holder of the engagement mechanism.
The engagement mechanism holder is designed to couple to the end plug assembly. Once assembled to the plug assembly the holder provides both an electrical contact and a mechanical coupling between the first and second assemblies. The holder consists of a molded body or case with locking slot tracks that engage the external tabs of the second or plug assembly. The holder also contains electrical socket conductors designed to accommodate prongs or pins at either end. The engagement mechanism consists of a lock engagement spring retained to the holder by a retention pin or set screw. The spring is generally V-shaped with arms extending outward but generally parallel to each other from the top of the V-shaped spring. The holder slides with respect to the end plug assembly
The mating of the plug end assembly to the base assembly causes the thrust spring within the thrust plunger to be compressed by the force exerted upon mating. As the end of the engagement mechanism holder contacts the innermost surface of the base assembly, the molded end plug assembly will move towards the base assembly and relative to the engagement mechanism holder. The range of relative movement that occurs between the molded plug and the engagement mechanism holder is limited by the length of the slots receiving the tabs on the end plug assembly. At the point where the lock engagement spring comes into contact with a slanted exterior shoulder of the second assembly, the locking engagement spring is forced to move outward where it is received in grooves on the interior surface of the first assembly cavity. As further pressure is applied, a flat exterior shoulder of the second assembly slips under the engagement spring arms thereby blocking the inward return of the arms thereby locking the engagement assembly to the first assembly. Known engineering design controls the side pinching force of the prong receptacles contacts and the lock engagement spring pressure against the outer flat exterior shoulder of the second assembly. The pressure of the thrust spring and the thrust spring plunger is transferred through the lock engagement spring into the first assembly housing. The thrust plunger maintains a potential energy stored in its compression spring for use upon release of the locking engagement spring. It will be appreciated that the spring locking force can be varied with the design requirements via spring parameter selection.
When a force above an minimum level is exerted on the cord, the molded plug or second assembly moves within the locking slot tracks of the locking assembly housing. After a small but predetermined amount of travel, the outer flat exterior shoulder is withdrawn sufficiently to permit the engagement spring to collapse into its original, relaxed or static position and out of engagement with the base recessed groove. With this action taking place no further locking pressure is retained. The stored force of the compressed thrust spring now pushes the thrust plunger to eject the entire second assembly and engagement housing. The thrust spring plunger acts over a length greater than the prongs of the base assembly. This action assures that the entire second assembly and engagement housing is completely ejected. The ejection terminates both physical and electrical contact between the first assembly and the entire second assembly and engagement housing combination.
Other features, aspects and advantages of this invention will become apparent from the following description of the preferred embodiment which references the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.